Self-heating and adhesive devices have been produced, for example, as follows:    1) bonding or heat-sealing a gas-permeable sheet and a gas-impermeable sheet to make a pouch having an opening;    2) stuffing an exothermic composition into the pouch;    3) closing the opening of the pouch by bonding or heat-sealing;    4) preparing a composite of a support and an adhesive poultice or gel whose surface is covered with a releasing sheet;    5) bonding an outer surface of the support to an outer surface of the gas-impermeable sheet by using an adhesive that has been applied to the gas-impermeable sheet; and    6) cutting off one self-heating and adhesive device.
The poultice or gel layer is commonly produced by applying an aqueous composition onto one surface of the support and then making water-soluble polymers contained in the composition closslink with crosslinking agents. However, when unwoven fabric is used as the support, the aqueous composition sometimes permeates through the unwoven fabric to get to the other side of it during the application, or after the application and before the completion of the closslinking. This is disclosed in Japanese Patent Early-publication No. 2000-119128. If the aqueous composition gets to the other side of the unwoven fabric, the adhesive force between the gas-impermeable sheet and the support, i.e., the unwoven fabric, lowers, which causes insufficient adhesion or the worst case where the gas-impermeable sheet and the support do not adhere to each other.
Self-heating and adhesive devices in which the adhesion between gas-impermeable sheet and the support is insufficient cannot be sold. Thus, if the aqueous composition permeates through the support to get to the other side of it, a yield factor lowers.
Japanese Patent Early-publication Nos. Hei. 08-336554, Hei. 10-152432, and Hei. 05-170644, each of which discloses an invention of a self-heating and adhesive device, show that there may be a support between an adhesive layer such as a poultice layer and a film or sheet that constitutes a part of an exothermic portion of the self-heating and adhesive device. However, they do not mention the permeation of the aqueous composition through the support and the lowering of the adhesive force that is caused by the permeation. Japanese Patent Early-publication No. Hei. 05-170644 shows that the support is adhered to the film or sheet that constitutes a part of an exothermic portion and then the adhesive layer such as the poultice layer is made on the support. Thus, by the method that is disclosed in Japanese Patent Early-publication No. Hei. 05-170644, the problem of the lowering of the adhesive force between the film or sheet and the support is not caused.
As a means for preventing the permeation of the aqueous composition through the support such as an unwoven fabric, it is proposed that an aqueous composition that will turn to the adhesive poultice or gel layer and that comprises a closslinking agent in a larger amount is used to closslink water-soluble polymers faster. By this means, the permeation of the aqueous composition may be surely prevented. However, if the closslinking agent is used in a large amount, the closslinking of the water-soluble polymers takes place over a long period of time and finally the poultice or gel layer becomes to nonadhesive. This means that the self-heating and adhesive device is insufficient in view of the storage stability.
An object of this invention is to prevent, by a means in which an amount of a closslinking agent is not increased, permeation of an aqueous composition through a support while an adhesive poultice or gel layer is made and aged.
Another object of this invention is to maintain the adhesiveness of the poultice or gel layer for a longer period of time.